The present invention relates to a vapor collection and disposal system and in particular relates to a gasoline vapor collection and disposal system.
During the refueling of motor vehicles in most standard gasoline stations, a significant amount of gasoline vapors are released into the atmosphere. Since gasoline vapors commonly consist of photochemically reactive hydrocarbons, upon exposure to sunlight, the vapors react with the oxides of nitrogen in the air to form air pollution.
Most prior efforts to solve this problem have involved the collection and disposal of the gasoline vapors. The vapors were normally disposed of by combustion or liquefication by compression and refrigeration. Unfortunately, in most cases, the vapors collected during the refueling operations comprised hydrocarbons and ambient air. In some cases, this lean vapor mixture may be in the explosive range. Therefore, it was essential that the hydrocarbon content of the vapor mixture be increased prior to liquefication or combustion to avoid explosions which may occur with the combustion or liquefication of a lean mixture of the hydrocarbon vapors. Prior methods of processing the vapors to increase the hydrocarbon content and to avoid explosions have involved the storage of the collected vapors over liquid hydrocarbon fuel or in tanks filled with carbon. These methods have involved the use of expensive equipment such as refrigeration units, pressurizing units, carbon adsorption units, etc. and in some cases have also involved extensive modification of the gasoline piping system to enable pressurization or evacuation of the system. One prior method for the recovery of gasoline vapors is disclosed in the Datis U.S. Pat. No. 3,972,201, the disclosure of which is incorporated herein by reference.
Another prior method of collecting and disposing of gasoline vapors is disclosed in the Hasselmann U.S. Pat. No. 3,999,936. The method disclosed in Hasselmann involves collecting the lean gasoline vapor during refueling operations and storing these vapors in the liquid gasoline storage tank to insure that the vapors are rich in hydrocarbons prior to processing. Upon reaching a predetermined pressure, the gasoline vapors are removed from the storage tank and passed into an incinerator where they are burned off. Unfortunately, if the vapors are left undisturbed in the storage tank for a period of time, the vapors will tend to stratify with the heavier hydrocarbons forming the lower layer and the ambient air being forced into the upper layer. Since the design of the Hasselmann system inherently requires that the vapor be drawn off from the top of the storage tank, in cases where the vapors have been left undisturbed in the storage tank for a period of time, a lean mixture of hydrocarbon vapors are passed to the incinerator. In some cases, this lean mixture may contain an explosive mixture of hydrocarbons and air. Therefore, an improved system for the collection and disposal of gasoline vapors s still required.